Commitments and Contingencies - Additional Information (Details)	1 Months Ended			12 Months Ended
	Nov. 30, 2015 USD ($) ft²	Dec. 31, 2014 USD ($) ft²	Dec. 31, 2013 USD ($) ft²	Dec. 31, 2015 USD ($) ft²	Dec. 31, 2014 USD ($) ft²
Commitments And Contingencies [Line Items]
Lease period			3 years
Area of property leased | ft²		8,530	6,837		8,530
Monthly lease payments		$ 45,000	$ 31,000	$ 32,000
Rent abatement			$ 31,000
Lease commenced and rental payments period			2014-01
Cash-collateralized irrevocable standby letter of credit			$ 125,345	$ 125,345
Lease space occupancy date		Mar. 13, 2015
Lease expiration date				Dec. 31, 2016
Landlord contribution for leasehold improvements		$ 100,000			$ 100,000
Additional cash security deposit paid to landlord		179,130			179,130
Rent expense associated with lease				$ 900,000	400,000
Contract cost incurred in research and development activities				5,200,000	4,300,000
Total cost of committed work not yet paid				$ 246,000,000
Office Equipment One
Commitments And Contingencies [Line Items]
Capital leases term				2 years
Capital lease commencement period				2014-02
Office Equipment Two
Commitments And Contingencies [Line Items]
Capital leases term				3 years
Capital lease commencement period				2015-04
Second Amendment
Commitments And Contingencies [Line Items]
Lease period				10 years
Area of property leased | ft²	23,189
Monthly lease payments	$ 107,000
Lease expiration date				Aug. 31, 2026
Additional cash security deposit paid to landlord	$ 976,382
Square feet of leased property | ft²	16,222
Operating lease payments commencement date				May 01, 2017
Second Amendment | Other Assets
Commitments And Contingencies [Line Items]
Additional cash security deposit paid to landlord		$ 304,475		$ 1,280,857	$ 304,475
Second Amendment | Delivered on November 23, 2015
Commitments And Contingencies [Line Items]
Monthly lease payments				$ 20,000
Square feet of leased property | ft²				3,066
Operating lease payments commencement date				Mar. 01, 2016
Second Amendment | Delivered on April 1, 2016
Commitments And Contingencies [Line Items]
Monthly lease payments				$ 110,000
Square feet of leased property | ft²				16,739
Operating lease payments commencement date				Sep. 01, 2016
Second Amendment | Delivered on January 1, 2017
Commitments And Contingencies [Line Items]
Monthly lease payments				$ 23,000
Square feet of leased property | ft²				3,384
Operating lease payments commencement date				May 01, 2017